title: Cell response to PEGylated poly(dopamine) coated liposomes considering shear stress.
abstract: BACKGROUND
  Liposomes have gained immerse attention in the field of drug delivery as carriers of therapeutic molecules. Their modification with a polymer either to make them stealth (e.g. using PEG) and/or more stable (e.g. using poly(dopamine) (PDA)) is a crucial aspect to improve their performance e.g. the blood circulation time. Despite their potential, there are only a few commercialized liposome-based formulations for intravenous drug delivery. Hence, there is still considerable need to address the challenges involved in the design and characterization of liposomal therapeutics. In the latter case, it is of paramount importance to consider the dynamic in vivo environment, e.g. the interstitial fluidic pressure in tumors, blood flow, or bile flow in the liver.
  
  
  METHODS
  The PEGylation of PDA films was characterized by quartz crystal microbalance with dissipation monitoring, and the optimized protocol was used to assemble PEGylated PDA coated liposomes (LPDA_PEG). Dynamic light scattering, a plate reader, a flow cytometer and a cytotoxicity assay were used to characterize the liposomes and quantify cellular association/uptake and cell viability in the presence and absence of shear stress after 30min and 4h. The immortalized skeletal mouse myoblast (C2C12) cell line was chosen as model cancer cells, and a hepatic cell line (HepG2) was selected due to their importance in nanosized drug carrier clearance from the system in the liver.
  
  
  RESULTS
  The presence of hydrophilic cargo did not affect the PDA assembly process. In the absence of shear stress, there was no difference in cellular uptake/association of both PDA coated liposomes (LPDA) and LPDA_PEG for hepatocytes while myoblasts preferentially internalized/associated with LPDA. In the presence of shear stress, hepatocytes preferentially internalized/associated with LPDA after 30min, while there was only a significant difference for myoblasts after 4h. The cell viability remained unaffected in all cases.
  
  
  CONCLUSIONS
  LPDA_PEG are a promising platform towards drug delivery. The nature of cells and fluidic flow are important factors to be considered in their characterization using cell cultures.
  
  
  CONCLUSIONS
  These findings will contribute in the better understanding of polymer coated liposomes with cells. The importance of microfluidics in cell culture based characterization is demonstrated, and this will eventually affect the way advanced drug delivery vehicles are designed and characterized prior to animal experiments.
authors.affiliation: Aarhus University, Aarhus, Denmark.
authors.forename: Boon M
authors.initials: BM
authors.lastname: Teo
authors.forename: Rebecca
authors.initials: R
authors.lastname: van der Westen
authors.forename: Leticia
authors.initials: L
authors.lastname: Hosta-Rigau
authors.forename: Brigitte
authors.initials: B
authors.lastname: Städler
mesh_terms: D000818:Animals; D002460:Cell Line; D003911:Dextrans / Q000737:chemistry; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000737:chemistry; D007211:Indoles / Q000737:chemistry*; D007700:Kinetics; D008081:Liposomes; D051379:Mice; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013312:Stress, Physiological
chemical_list: D003911:Dextrans; D007211:Indoles; D008081:Liposomes; D011108:Polymers; C015219:fluorescein isothiocyanate dextran; C568283:polydopamine; D011092:Polyethylene Glycols; D016650:Fluorescein-5-isothiocyanate
keywords: Liposomes; Microfluidics; PEGylated liposomes; Polydopamine; Shear stress